1. Field of the Invention
The present invention relates to a chuck apparatus which is employed in a working machine such as a spinning machine and which holds a workpiece or a working tool.
2. Discussion of Related Art
There is known a chuck which is attached to a spindle or a main shaft of, e.g., a working lathe or an external cylindrical grinding machine to hold a workpiece, or a main shaft of, e.g., a milling machine or a drilling machine to hold a working tool. Though there are known various sorts of chucks, two sorts of chucks are particularly known in the art, i.e., (a) a three-jaw chuck which includes a main member and three holding jaws which are movable in respective radial directions of the main member, and (b) a collet chuck which includes a collet having a generally tubular shape, having a plurality of expanding slots extending in an axial direction thereof, and having one of an outer tapered surface and an inner tapered surface and additionally includes a main member having one of an inner tapered surface and an outer tapered surface that corresponds to the one tapered surface of the collet.
A conventional chuck apparatus includes, in addition to a chuck, a state switching device which selectively switches the chuck to a work-hold state in which the chuck holds a work and a work-release state in which the chuck releases the work. As the state switching device, there are known a manually operable one and a power-driven one. In the case where the chuck is not a rotary one, the state switching device used with the chuck may be of a more or less large size. However, in the case where the chuck is a rotary one that is attached to a main shaft and is rotated with the main shaft, there is a strong need to reduce the size of the chuck apparatus. In particular, the power-driven state-switching device is likely to have a large size, which results in various sorts of disadvantages. For example, if the chuck apparatus which is rotated with the main shaft has a large size, then the apparatus has a great moment of inertia, which makes it difficult to start and stop quickly the rotation of the main shaft and thereby makes it difficult to improve the working efficiency of the working machine. In addition, it is difficult for the working machine to secure a space sufficient to accommodate the large-size chuck apparatus. This problem becomes more serious in the case where a working machine as a whole is of a considerably small size or a single working machine employs a plurality of spindles or main shafts each of which is associated with a chuck apparatus.
Meanwhile, in the case where the state switching device is a power-driven one, it has been conventional that the power-driven state-switching device employs, as a power source thereof, a hydraulically-operated cylinder device. However, the hydraulic cylinder device has a problem that the operation of the cylinder device cannot be finely controlled, in particular, the operation stroke thereof cannot be accurately controlled. In addition, the working machine which employs the chuck apparatus needs to employ a stand which produces a hydraulic pressure. Thus, the size and cost of the working machine are increased. Moreover, since the hydraulic-pressure stand needs to be continuously operated during the operation of the working machine, the energy efficiency of the machine is decreased.
The present invention provides a chuck apparatus and a working machine which have one or more of the following technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (18). Any technical feature that includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. However, the following technical features and the appropriate combinations thereof are just examples to which the scope of the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, . . . , but not all) of those items.
(1) According to a first feature of the present invention, there is provided a chuck apparatus comprising a chuck; and a power-driven device which selectively places the chuck in an object-hold state thereof in which the chuck holds an object, and an object-release state thereof in which the chuck releases the object, the power-driven device comprising, as a power source thereof, an electric motor.
Since the power-driven device which selectively places the chuck in the object-hold state and the object-release state includes, as the power source, the electric motor, the present chuck apparatus is free of the above-identified problems and/or disadvantages of the conventional chuck apparatus in which the power-driven device includes, as the power source, the hydraulic cylinder device.
(2) According to a second feature of the present invention that includes the first feature (1), the electric motor comprises a servomotor.
Since the servomotor as the electric motor can be accurately controlled with respect to its rotation angle, torque, rotation speed, etc, an operation amount, and an operation force, of the chuck apparatus can be finely controlled.
(3) According to a third feature of the present invention that includes the first or second feature (1) or (2), the chuck comprises at least one holding member at least a portion of which is moved in a radial direction thereof so as to be selectively placed in the object-hold state and the object-release state, the power-driven device further comprises an axial-direction movable member which is movable in an axial direction of the chuck; and a first motion converting device which converts the axial-direction motion of the movable member into the radial-direction motion of at least the portion of the holding member, and the electric motor causes the axial-direction motion of the movable member.
(4) According to a fourth feature of the present invention that includes the third feature (3), the axial-direction movable member comprises a draw bar which transmits a tensile force to the chuck and thereby places the chuck in the object-hold state.
Since the chuck apparatus employs the draw bar, it is made possible to attach the chuck to a front end of a rotary shaft, such as a spindle, and provide the power source of the power-driven device around a rear end of the rotary shaft. Thus, it is made easier to dispose the power-driven device as a whole or the power source thereof. Since a tool rest or a work rest which is moved while holding a tool or a work is provided around the chuck, it is difficult, in many cases, to dispose the power-driven device around the chuck. However, the present chuck apparatus is free of that problem.
(5) According to a fifth feature of the present invention that includes the third or fourth feature (3) or (4), the power-driven device further comprises a first rotary member which is rotatable about an axis line of the axial-direction movable member and whose axial-direction movement is restricted; and a second motion converting device which converts the rotary motion of the first rotary member into the axial-direction motion of the movable member, and the electric motor rotates the first rotary member.
In the present chuck apparatus, since the rotation of the first rotary member causes the axial-direction movement of the axial-direction movable member, the rotary-type electric motor can be easily employed as the power source of the power-driven device.
(6) According to a sixth feature of the present invention that includes the fifth feature (5), the second motion converting device comprises a first threaded member which is substantially integral with the axial-direction movable member and a second threaded member which is threadedly engaged with the first threaded member, and the second threaded member is substantially integral with the first rotary member. The phrase xe2x80x9csubstantially integralxe2x80x9d means either the first or second threaded member is literally integral with the axial-direction movable member or the first rotary member, or that the former member is fixed to the latter member such that the two members are not movable or rotatable relative to each other.
Since the second motion converting device includes the first and second threaded members which are threadedly engaged with each other, the construction of the present chuck apparatus can be easily simplified.
(7) According to a seventh feature of the present invention that includes the fifth or sixth feature (5) or (6), the power-driven device further comprises a clutch which is provided between the electric motor and the first rotary member and which is selectively placed in a connected state thereof in which the clutch connects the first rotary member and the electric motor to each other and a disconnected state thereof in which the clutch disconnects the first rotary member and the electric motor from each other, the clutch being usually kept in the disconnected state, and being placed in the connected state when the chuck is switched between the object-hold state and the object-release state.
Though the chuck is of a type which is rotated with the rotary shaft, at least the power source of the power-driven device can be disconnected from the chuck, by placing the clutch in the disconnected state. Thus, the power source need not be rotated with the rotary shaft. This feature contributes to increasing the degree of freedom with respect to the position where the electric motor is disposed, or reducing the moment of inertia exerted to the chuck and a portion of the power-driven device that is rotated with the rotary shaft. However, it is noted that the seventh feature (7) may be employed in a chuck apparatus which employs a hydraulic oscillating motor as the power source of the power-driven device.
(8) According to an eighth feature of the present invention that includes any one of the fifth to seventh features (5) to (7), the power-driven device further comprises at least one elastic member which applies an elastic force to the first rotary member in a direction in which the chuck is biased toward the object-hold state via the axial-direction movable member and the second motion converting device.
When the elastic force of the elastic member is applied to the first rotary member, the elastic force is transmitted to the axial-direction movable member via the first rotary member and the second motion converting mechanism, so that the chuck is stably kept in the work-hold state. This feature is particularly advantageous in the case where a clutch is provided between the electric motor and the first rotary member and the clutch is placed in its disconnected state during the rotation of the rotary shaft.
(9) According to a ninth feature of the present invention that includes any one of the third to eighth features (3) to (8), the chuck comprises a main member and three holding members which are supported by the main member such that the holding members are movable in respective radial directions of the main member, and the first motion converting device converts the axial-direction motion of the movable member into respective radial-direction motions of the three holding members that are axis-symmetric with one another with respect to an axis line of the main member.
The holding members may be ones which cooperate with one another to engage an outer circumferential surface of an object and thereby hold the object, or ones which cooperate with one another to engage an inner circumferential surface of an object and thereby hold the object.
(10) According to a tenth feature of the present invention that includes any one of the third to eighth features (3) to (8), the holding member comprises a collet which has a tubular shape and has a plurality of slots extending in the axial direction of the chuck, and the first motion converting device comprises one of an outer tapered surface and an inner tapered surface that is provided on the collet; and a main member which has the other of the inner tapered surface and the outer tapered surface.
The collet may be one which engages an outer circumferential surface of an object and thereby hold the object, or one which engages an inner circumferential surface of an object and thereby hold the object.
(11) According to an eleventh feature of the present invention that includes any one of the first to tenth features (1) to (10), the chuck comprises a main member which is attached to an end of a rotary shaft so as to be rotated with the rotary shaft.
(12) According to a twelfth feature of the present invention that includes the eleventh feature (11), the electric motor is attached to a frame which supports the rotary shaft such that the rotary shaft is rotatable about an axis line thereof.
(13) According to a thirteenth feature of the present invention that includes the eleventh or twelfth feature (11) or (12), the chuck apparatus further comprises a main drive device which rotates the rotary shaft.
(14) According to a fourteenth feature of the present invention that includes the thirteenth feature (13), the main drive device comprises a second electric motor which is different from the electric motor of the power-driven device as a first electric motor and which includes a stator fixed to the frame; and a rotor which is provided inside the stator such that the rotor is coaxial with the stator and which is fixed to the rotary shaft so as to be rotated with the rotary shaft.
Since the rotation of the rotor is directly transmitted to the rotary shaft, it is possible to reduce the moment of inertia that is exerted to the chuck and a portion of the power-driven device that is rotated with the rotary shaft.
(15) According to a fifteenth feature of the present invention that includes the seventh feature (7), the clutch comprises a first clutch member which is fixedly provided on the first rotary member; and a second clutch member which is coaxial with the rotary shaft, is rotatable relative to the rotary shaft, and is movable relative to the rotary shaft in the axial direction of the chuck, and which is moved in the axial direction to be engaged with, and disengaged from, the first clutch member.
The present chuck apparatus can employ any one of the eighth to fourteenth features (8) to (14).
(16) According to a sixteenth feature of the present invention that includes the fifteenth feature (15), the chuck apparatus further comprises a frame; a rotary shaft which is supported by the frame such that the rotary shaft is rotatable about an axis line thereof; a main member which is attached to an end of the rotary shaft; a second rotary member which is supported by the frame such that the second rotary member is rotatable about an axis line thereof and which is engaged with the second clutch member such that the second rotary member is not rotatable relative to the second clutch member and is movable relative to the second clutch member in the axial direction of the chuck; and a rotation transmitting member which transmits the rotation of the electric motor to the second rotary member.
For example, the second rotary member is provided by a pulley, and the rotation transmitting member is provided by a wound-on member, such as a belt or a chain, that is wound on the pulley. Alternatively, the second rotary member may be provided by a first gear, and the rotation transmitting device may be provided by a second gear which is meshed with the first gear.
(17) According to a seventeenth feature of the present invention, there is provided a working machine comprising a frame; a rotary shaft which is supported by the frame such that the rotary shaft is rotatable about an axis line thereof relative to the frame; a rotor which is fixed to the rotary shaft; a stator which is provided outside the stator such that the stator is coaxial with the rotor and which is supported by the frame such that the stator is not rotatable relative to the frame; and a chuck which is provided at an end of the rotary shaft and which holds and releases an object.
The object may be either a workpiece or a working tool. In the case where the object is a workpiece, the present working machine further employs a too holding device which is not rotatable and which holds a working tool. On the other hand, in the case where the object is a working tool, the present working machine further employs a workpiece holding device which is not rotatable and which holds a workpiece. The present working machine may employ any one of the first to sixteenth features (1) to (16).
(18) According to an eighteenth feature of the present invention that includes the seventeenth feature (17), the working machine further comprises a state switching device which includes a power source and which selectively switches the chuck to an object-hold state thereof in which the chuck holds the object and an object-release state thereof in which the chuck releases the object, the power source is separate from the rotary shaft and is not rotatable relative to the frame.